Research And Application Of Single-Phase Power Distribution Technology

ABSTRACT: In recent years, state grid corporation of china stresses the development and application of single-phase distribution technology. The research and development of single-phase transformer is continually driven in urban and rural distribution network. The single-phase distribution mode is tested and will be compatibly applied in the mid and low voltage distribution network of suburb and county where the load density is not too high. It is highlighted that the high voltage side is closed to the users and the length of low voltage lines is evidently shorted. And the mode has the distribution advantages that the capacity is small, distribution points are dense and radius is short. Through the distribution mode is adopted, the line loss rate is observably reduced, the reliability of power supply and voltage quality are improved. It has good technical and economical performances and adapts to the load development. A good many problems related to the single-phase distribution technology have become the hot research task.In the beginning of the thesis, according to field investigation, analysis and research, combined with the real status of power distribution system in our country, several single-phase distribution modes are given, which can steadily run at the present period and can be applied to urban and rural distribution system.The coupling circuit relation of single-phase and double winding transformer is analyzed. The two-port circuit mode of the single-phase transformer is built. Then load flow calculations of single-phase distribution can be achieved. According to its characteristics, U-I-PARS type of forward and backward substitution method is adopted for power flow calculation, of which the voltage is amended in the forward process and only the current is amended in the back substitution process.The single-phase power supply mode is easy to prone to the problem of imbalance with a three wire because of load dispersion and long-distance. On the basis of power flow calculation above, three phases imbalance can be reformed by changing single phase load spicing phase sequence. Based on enumeration method, the single-phase load spicing plan with minimal changes in which three-phase balance degree is the best is determined to effectively improve the three-phase imbalance degree in single-phase distribution mode.At last the reform program of single-phase power supply is designed for a type community with three-phase power supply where low voltage line loss is high and voltage quality is low. The investment and loss are analyzed under two power supply modes. The economics advantages of single-phase power supply plan compared with three-phase power supply plan are verified using the method of calculating investment recovery period. Then the power flow calculation is done adopting the forward computation methods and the best single-phase load spicing plan is chosen based on single-phase load spicing transformation method, which comprehensively verifies the advantages of single-phase distribution technology. The result shows that the proposed modes and algorithms are effective and practical, which provides technical support to promote application of single-phase power supply technology.